This invention relates to precision winders such as are used in the repackaging of strand materials such as textile thread and yarns.
In certain manufacturing processes, such as the manufacture of sewing thread, it is conventional to repackage strands by an operation known as winding, performed on apparatus known as winders. Certain winders, capable of high speed and controlled winding, are known as precision winders. An early example of a precision winder is the Leesona Model 50, shown for example in Bell U.S. Pat. No. 2,608,355. A more recent example is the Ott NGS 10, manufactured by A. Ott of Kempten, Germany. More detailed information regarding such apparatus and the methods of operation inherent in them can be obtained from the aforementioned Patent and from industry sources such as trade publications. Generally speaking, such winders may be characterized as having provision for one or more supply packages of strand material, a take-up package about which strand material is to be wound, and guide means for guiding strand material from a supply package to the take-up package.
One of the important economic justifications for the use of precision winders of the types described lies in the speed of operation of the winders and the capability of the winders to achieve desired package characteristics. While such apparatus and methods as have been known heretofore have achieved acceptance within the industries where they are used, precision winders of the types mentioned above encounter certain problems. In particular, such winders encounter limitations on the speed of strand movement and on the coordination of tension imposed on the strand during winding. Heretofore, the usual design comprises with respect to speed have been to select a limiting strand speed or velocity at the extreme capability of the state of the art and then design the drive for the take-up package to operate at a constant rotational speed calculated to provide the limiting strand speed at the greatest anticipated diameter of the take-up package. The usual design with respect to strand tension has been to attempt to achieve a uniform strand tension throughout winding. As a result of these choices, strand speed or velocity during the early stages of a package build, or while the diameter of the take-up package is relatively small, is usually well below the limiting speed. Further, attempts to maintain a uniform strand tension throughout package building usually results in a "hard" package in which the outer layers of strand material are so tightly wound that excessive compressive forces are exerted on the inner layers and of any core about which the package is wound. In some instances, such forces have been known to crush the package cores, and to otheriwse interfere with unwinding of the strand material.